The present invention relates to a transmission device effecting light transmission, and in particular to modules in charge of light transmission and light reception in the transmission device.
Recently, repletion of communication networks has become more and more important with development of the post-industrial society.
Thus, an SDH transmission system, etc. is being introduced, which consists of a new digital hierarchy network composed principally of light transmission paths of 156 Mb/s.times.n constructed by new synchronized terminal devices having network node interfaces (NNI) in conformity to the CCITT recommendation, described, e.g., in "Trend of development of systems contributing to construction and improvement in operability of a transmission network (in Japanese)" published in the NTT Journal (January 1992), etc.
However, each transmission device used in such systems should have a "multiplexing function" putting a plurality of low speed signals together into a high speed signal, a "cross connect (line path compilation) function" separating and collecting multiplexed signals, a "signal converting function" between a low speed interface and an SDH interface, etc., as indicated in FIGS. 16A to 16C, respectively. In order to realize such a "multiplexing function", a "cross connect (line path compilation) function" and a "signal converting function", each transmission device should be provided with a transmitting circuit effecting transmitting processing including electro-optical converting processing and a receiving circuit effecting receiving processing including opto-electrical converting processing.
Heretofore, a transmitting module, in which such a transmitting circuit is realized in the form of a module, and a receiving module, in which a receiving circuit is realized in the form of a module independently therefrom, have been used in a transmission node.
As a technique relating to this kind of light transmission modules there is known a technique described in JP-A-Sho 59-180514.